Testing methods for direct measurement of particle settling velocities and fluxes in the sea

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Sediment traps are widely used to quantify vertical fluxes of material and to collect sinking particulate organic matter (POM) for chemical analyses. They have provided proof of spatial, episodic, seasonal, and interannual fluxes of POM through the water column, have linked variability in surface water processes to fluxes in the interior of the ocean and to the sea floor, and have shown that intense remineralization and alteration affects POM in the water column. In this project, researchers at the State University of New York at Stony Brook will modify a settling velocity trap developed recently as part of the MedFlux Program by installing cameras above and below the rotating ball valve to monitor particle settling rates as they fall into the trap and after the ball rotation. These measurements should allow them to unequivocally determine whether particles are combining on the ball to produce artificially-high settling velocities, or if the previous settling velocity estimates are truly robust.Broader Impacts: Testing and development of the settling velocity traps will ideally allow for in situ measurements of particle settling rates that in turn provide critical constraints on elemental cycling within the water column. Collected samples will also allow assessment of the relative importance of various ballast materials (e.g., carbonate, opal, etc.). While the trap development is important to our understanding of the biological pump, the ability to better understand carbon fluxes also has a direct impact on larger societal issues such as CO2 concentrations in both the oceans and the atmosphere.